1 .\" $KAME: getaddrinfo.3,v 1.36 2005/01/05 03:23:05 itojun Exp $
2 .\" $OpenBSD: getaddrinfo.3,v 1.35 2004/12/21 03:40:31 jaredy Exp $
4 .\" Copyright (C) 2004 Internet Systems Consortium, Inc. ("ISC")
5 .\" Copyright (C) 2000, 2001 Internet Software Consortium.
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27 .Nd socket address structure to host and service name
34 .Fa "const char *hostname" "const char *servname"
35 .Fa "const struct addrinfo *hints" "struct addrinfo **res"
38 .Fn freeaddrinfo "struct addrinfo *ai"
42 function is used to get a list of
44 addresses and port numbers for host
48 It is a replacement for and provides more flexibility than the
58 arguments are either pointers to NUL-terminated strings or the null pointer.
59 An acceptable value for
61 is either a valid host name or a numeric host address string consisting
62 of a dotted decimal IPv4 address or an IPv6 address.
65 is either a decimal port number or a service name listed in
74 is an optional pointer to a
80 int ai_flags; /* input flags */
81 int ai_family; /* protocol family for socket */
82 int ai_socktype; /* socket type */
83 int ai_protocol; /* protocol for socket */
84 socklen_t ai_addrlen; /* length of socket-address */
85 struct sockaddr *ai_addr; /* socket-address for socket */
86 char *ai_canonname; /* canonical name for service location */
87 struct addrinfo *ai_next; /* pointer to next in list */
91 This structure can be used to provide hints concerning the type of socket
92 that the caller supports or wishes to use.
93 The caller can supply the following structure elements in
95 .Bl -tag -width "ai_socktypeXX"
97 The protocol family that should be used.
102 it means the caller will accept any protocol family supported by the
105 Denotes the type of socket that is wanted:
112 is zero the caller will accept any socket type.
114 Indicates which transport protocol is desired,
120 is zero the caller will accept any protocol.
126 parameter points shall be set to zero
127 or be the bitwise-inclusive OR of one or more of the values
134 .Bl -tag -width "AI_CANONNAMEXX"
138 bit is set, IPv4 addresses shall be returned only if
139 an IPv4 address is configured on the local system,
140 and IPv6 addresses shall be returned only if
141 an IPv6 address is configured on the local system.
145 bit is set, a successful call to
147 will return a NUL-terminated string containing the canonical name
148 of the specified hostname in the
153 .It Dv AI_NUMERICHOST
156 bit is set, it indicates that
158 should be treated as a numeric string defining an IPv4 or IPv6 address
159 and no name resolution should be attempted.
160 .It Dv AI_NUMERICSERV
166 string supplied shall be a numeric port string.
169 error shall be returned.
170 This bit shall prevent any type of name resolution service
171 (for example, NIS+) from being invoked.
175 bit is set it indicates that the returned socket address structure
176 is intended for use in a call to
180 argument is the null pointer, then the IP address portion of the
181 socket address structure will be set to
183 for an IPv4 address or
189 bit is not set, the returned socket address structure will be ready
192 for a connection-oriented protocol or
197 if a connectionless protocol was chosen.
200 address portion of the socket address structure will be set to the
203 is the null pointer and
209 All other elements of the
213 must be zero or the null pointer.
219 behaves as if the caller provided a
225 and all other elements set to zero or
228 After a successful call to
231 is a pointer to a linked list of one or more
234 The list can be traversed by following the
238 structure until a null pointer is encountered.
241 structure contains three members that are suitable for a call to
249 structure in the list, the
251 member points to a filled-in socket address structure of length
254 This implementation of
256 allows numeric IPv6 address notation with scope identifier,
257 as documented in chapter 11 of RFC 4007.
258 By appending the percent character and scope identifier to addresses,
262 This would make management of scoped addresses easier
263 and allows cut-and-paste input of scoped addresses.
265 At this moment the code supports only link-local addresses with the format.
266 The scope identifier is hardcoded to the name of the hardware interface
278 on the link associated with the
283 The current implementation assumes a one-to-one relationship between
284 the interface and link, which is not necessarily true from the specification.
286 All of the information returned by
288 is dynamically allocated: the
290 structures themselves as well as the socket address structures and
291 the canonical host name strings included in the
295 Memory allocated for the dynamically allocated structures created by
305 structure created by a call to
309 returns zero on success or one of the error codes listed in
313 The following code tries to connect to
318 It loops through all the addresses available, regardless of address family.
319 If the destination resolves to an IPv4 address, it will use an
322 Similarly, if it resolves to IPv6, an
325 Observe that there is no hardcoded reference to a particular address family.
326 The code works even if
328 returns addresses that are not IPv4/v6.
329 .Bd -literal -offset indent
330 struct addrinfo hints, *res, *res0;
333 const char *cause = NULL;
335 memset(&hints, 0, sizeof(hints));
336 hints.ai_family = PF_UNSPEC;
337 hints.ai_socktype = SOCK_STREAM;
338 error = getaddrinfo("www.kame.net", "http", &hints, &res0);
340 errx(1, "%s", gai_strerror(error));
344 for (res = res0; res; res = res->ai_next) {
345 s = socket(res->ai_family, res->ai_socktype,
352 if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
359 break; /* okay we got one */
368 The following example tries to open a wildcard listening socket onto service
370 for all the address families available.
371 .Bd -literal -offset indent
372 struct addrinfo hints, *res, *res0;
376 const char *cause = NULL;
378 memset(&hints, 0, sizeof(hints));
379 hints.ai_family = PF_UNSPEC;
380 hints.ai_socktype = SOCK_STREAM;
381 hints.ai_flags = AI_PASSIVE;
382 error = getaddrinfo(NULL, "http", &hints, &res0);
384 errx(1, "%s", gai_strerror(error));
388 for (res = res0; res && nsock < MAXSOCK; res = res->ai_next) {
389 s[nsock] = socket(res->ai_family, res->ai_socktype,
396 if (bind(s[nsock], res->ai_addr, res->ai_addrlen) < 0) {
401 (void) listen(s[nsock], 5);
417 .Xr gethostbyname 3 ,
419 .Xr getservbyname 3 ,
432 .%T Basic Socket Interface Extensions for IPv6
442 .%T "IPv6 Scoped Address Architecture"
448 .%T Protocol Independence Using the Sockets API
449 .%B "Proceedings of the freenix track: 2000 USENIX annual technical conference"
455 function is defined by the
457 specification and documented in
459 .Dq Basic Socket Interface Extensions for IPv6 .